Apparatus for roasting fusible ores.



PATENTED SEPT. 17, 1907.

A. G. DAVIS. APPARATUS FOR ROASTING FUSIBLE ORBS.

API LIOATION FILED MAR. 26, 1902.

UNITED STATES PATENT OFFICE.

ALBERT GOULD DAVIS, OF SGI-IENEOTADY, NEW YORK.

APPARATUS FOR ROASTING FUSIBLE ORES.

Specification of Letters Patent.

Patented Sept. 17, 1907.

Original application filed September 12, 1896, Serial No. 605,625. Divided and this application filed March 26, 1902. Serial No. 100.058.

To all whom it may concern: Be it known that I, ALBERT GOULD Davis, a citizen of the United States, residing at Schenectady, county of V Schenectady, State of New York, have invented certain tain impurities, particularly sulfur.

A large supply of oxygen is essential to the thorough desulfurization of ores. If a piece of FeS be heated in a mattrass to a high temperature, it will give off about one half of its sulfur as vapor, and there the operation will cease; even if the mattrass be heated to temperatures far above those which can be employed in commercialroastin g, there will be a strong tendency to retain the last atom of sulfur, and for the resulting compound to be, practically FeS. If new a similar piece of F eS be heated in an open tube with air passing over it, the sulfur will be driven off, and an oxid of iron will remain.

Ores of copper, and many other ores in commercial use, contain large percentages of sulfur, sometimes existing as FeS mechanically combined with the ore, and in most cases occurring as compounds which, although more complex, are of the same order, that is to say are high in sulfur and fusible. It has been proposed to roast such ores by heating them to high temperatures in an oxidizing flame, and passing cold air across them when the temperature attained was so high that there was danger of fusion. This process is commercially successful on many ores, such as certain ores of iron in which the percentage of sulfur is low, and will work well up to five per cent. of sulfur, or even more. But above a certain percentage air ceases to cool the ore, as the heat liberated chemically by the combustion of the sulfur and iron with the oxygen of the air is greater than that absorbed in dissociating the FeS and mechanically abstracted by the cool air. Such ores may be said to burn with their own heat, and for such this process fails. If however the FeS remaining in the mattrass, in the experiment above described, be examined, it will be found to be porous, filled with openings where the sulfur has boiled out, and also highly infusible. The same condition will be observed if for FeS We substitute ores as of copper, high in sulfur, though the reaction in that case may not be so simple. To treat such ores I therefore use a double process; I first heat them above the boiling point of sulfur, in a practically closed chamber at an even temperature and in a reducing flame, or at least in the nearly complete absence of free oxygen. Part of the sulfur boils off, leaving a porous infusible compound of the FeS order. The ore cannot fuse during this stage of the process, as the temperature is too low and oxygen is carefully excluded. But when this stage is over the ore is in a condition where it ceases to burn with its own heat, and where it may be safely exposed to high temperatures and oxidizing flames. I therefore now pass over or through it, preferably the latter, a current of highly heated gases containing an excess of oxygen, which gases rapidly burn out the remaining sulfur and leave oxids of iron and of sulfur. The latter are carried off bya suitable draft arrangement, and the oxids of iron, which constitute with the various substances mixed with them the roasted ore, are withdrawn.

Though I have described this process as applied to ores containing the sulfid of iron, it is not limited to that use, but applies to any substance whatever which possesses the characteristics above described.

My present application, which is a division of my former application, Serial Number 605,625, is restricted to a furnace which is capable of carrying out this process, though adapted to other uses.

In the first stage of the process above described it is important that the temperature be fairly even and uniform; I therefore prefer to pass the gases which carry the heat to the ore in this stage through a chamber filled with broken stone or fire brick, checker work, or other substance capable of withstanding the temperatures used, and of absorbing and giving up heat. This also tends to give more perfect combustion.

In the drawing annexed to this specification, Figure l is an elevation section of my improved kiln on the line 1-1 of Fig. 2. Fig. '2 is a half horizontal cross section on the line 2-2 of Fig. 1.

In the figures, 11, 12 and 13 are circular walls, inclosing the exit chamber 14, the ore chamber 15, and the upper combustion chamber 16.

17 is a circular wall inclosing the lower part of the chamber 16, while the annular space 18 between the walls 17 and 13 is the lower combustion chamber. Gas is admitted to the arches 19, 20, by the fines 21, 22, respectively, and burns in the arches and combustion chambers. The arch l9 communicates with the chamber 16, while the arch 20 communicates with the chamber 18. Air is admitted through the doors 23, 24, and also if desired through the air flucs 25, 26. The fines 25, 26, may be supplied with air,under pressure, but I prefer to simply lead them to the outer air, and provide them with valves 25 26 The gas fines are piped to a suitable source of gas, and preferably provided with cleaning doors 21 22, and suitable valves. The ore is fed at the top, in the space 27, and passes through the ore space 15, being drawn-out at the chutes 28.

The two combustion chambers are separated from each other by the wall17, and the hopper 29, while they communicate with the ore space through the ports 30, 31. The ore space is connected with the exit space 14 by the ports 32 in the wall 12.

Gas burns at the arch 19 with a small amount of air, producing a strongly reducing llame, which passes through the checker work 35 to the chamber 16, through the upper portion of the ore space 15, through the ports 32 to the exit space 14, and thence through the ports 33, 33, to the collection flue 34, and thence to the draft stack. The checker Work serves the purpose of equalizing the temperature of the burned and burning gases, aids combustion by setting'up eddy currents, and prevents any irregularity of heat in different parts of the upper portion of the ore space. This latter effect is important, as the ore is there in its most fusible condition. Gas also burns at the arch 20, but in this arch it is supplied with an excess of air, giving an oxidizing flame, which passes through the chamber 18, thence through the ports 30, the ore space 15, and out as before. Though I prefer to burn gas, as it is very easy to regulate and control, any other fuel, as oil, coal, or wood, may be employed with suitablechanges in the lire arches l9 and 20.

It is obvious that the collected gases contain large amounts of sulfur, which may be collected and used for the manufacture of sulfuric acid and for other purposes. As the gases resulting from the two stages of the process are of different chemical compositions, I may divide the exit chamber into two or more horizontal divisions as indicated by the dotted lines 40, and take the different mixtures out separately.

Cleaning arches, as 36, are provided where required, and the exit space 14 is provided with cleaning ports 37. "he space at the top is preferably closed by the cone 38, and the whole kiln should be surrounded by a wrought iron or steel shell 39, with a proper expansion space as shown.

It should be distinctly understood that I do not limit myself to the use of a reducing atmosphere in the first stage of the process, as a small quantity of oxygen, though objectionable in most cases, is not necessarily fatal to the process.

Though it is preferable to use a highly heated gas in the last half of the process, it is not essential; as mere exposure of the heated ore to a current of air will remove large quantities of the remaining sul'ur.

Though I have shown a circular kiln, which is the preferred form, I do not limit myself thereto, as my furnace may be built in many forms. "he kiln which I have shown is not only useful for carrying out my process, but may be used for ordinary roasting, calcining, etc. and for many other purposes, particularly where it is desired to expose the material under treatment to different temperatures and conditions during different parts of the operation. I therefore do not limit myself to the particular forms shown and described.

The various methods disclosed in this specification are not herein claimed, but are claimed in my pending application,'Serial No. 605,625, .filediSept. 12, 1896, of which this case is a division.

What I claim as new and desire to secure by'Letters Patent of the United States is:

1. In an ore roasting or calcining furnace, the combination of four annular walls inclosing an annular exit chamber, an ore space, two combustion chambers, ports connecting the ore space with the exit chamber, and ports connecting the combustion chambers with the ore space, substantially as described.

2. In an ore roasting or calcining furnace the combination of an annular ore space, an exit chamber outside of said ore space, ports connecting the ore space with the exit chamber, .and two combustion chambers, in communi cation respectively with different parts of said ore space,-

substantially as described.

In an ore roasting or calcining furnace the combination of an annular ore space, two combustion chambers inclosed and surrounded laterally by the inner wall of said ore space and connected with the ore space, and means for the exit from the ore space of products of combustion, substantially as described.

4. in an ore roasting or calcining furnace, the combi nation of an annular ore space, a central combustion chamber and an annular combustion chamber, both in connection with said ore space, and means for the exit from the ore space of products of combustion, substantially as described.

5. In an ore roasting or calcining furnace, the combination of an annular ore space, an annular combustion chamber inside said ore space, a central combustion chamher inside said annular combustion chamber at its lower part only and for its whole length inside said ore space, an annular exit chamber outside of and laterally surrounding the ore space, and ports connecting said ore space with the combustion chamber and the exit chamber, substan tially as described.

6. In an ore roasting or calcining furnace the combination of an ore space, two combustion chambers in connection respectively with different parts of said ore space, and means for the exit from the ore space of products of combustion, with masses of material capable of absorbing and giving out heat placed across one of said combustion chambers, substantially as described.

7. in an ore roasting 01' calcining furnace the combi nation of an annular ore space, two combustion chambers iuclosed and surrounded laterally by the inner wall of said ore space, in direct connection respectively with different parts of said ore space, burners for said combustion chambers, means for the exit from the ore space of products of combustion, and masses of material capable of absorbing and giving out heat placed in the path of the gases from one of said burners, substantially as described.

8. In an ore-roasting or calcining furnace, the combination of an annular ore space, an annular combustion chamber, a central combustion chamber inside said annular combustion chamber at its lower part only and for its whole length inside said ore space, the combustion chambers being in connection with the ore space at different heights, and an annular exit chamber outside of and laterally surrounding said ore space and in connection therewith, with masses of material capable of absorbing and giving out heat placed in that one of said combustion chambers in communication with the upper portion of the ore space, whereby the temperature in the upper portion of the ore space is equalized and regulated, substantially as described.

In witness whereof I have hereunto set my hand this 20th day of March, 1902.

ALBERT GOULD DAVIS.

Witnesses BENJAMIN B. HULL, HELnN ORFORD. 

